This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not admissions regarding what is or is not prior art.
Semiconducting nanoparticles (NPs) are useful in such practical applications as electronics, light emitting diodes, sensors, thermoelectrics, solar cells, and the like. By suspending NPs in a solvent, a NP “ink” can be formulated, enabling printing or spray coating of semiconducting compounds and allowing a roll-to-roll manufacturing route and potentially reducing production costs. For example, earth abundant solar absorber materials produced from NP inks offer a low cost and highly scalable route to solar cell production, compared to vacuum processing. Thin film formation via nanoparticle dispersion also enables production of flexible materials and devices.
Nanoparticle based devices offer additional tunability and subsequent performance enhancement through exploitation of the quantum confinement effect (QCE) and relevant chemistry related to high surface area materials. More specifically, thermoelectric device performance such as carrier concentration and thermal conductivity can be optimized via control of the nanocrystal morphology, as this can act as phonon scattering centers. By using a nanoparticle framework, these parameters can be controlled, enabling low cost optimization of thermoelectric properties with highly scalable, solution processable production.
By themselves, NP films do not typically provide high performance due to extremely low carrier transport properties, which are typically circumvented by spark plasma sintering or hot pressing. These sintering methods, while greatly increasing device performance, offer limited scalability of these types of thermoelectric devices.
One material commonly utilizing such sintering methods is the Cu3SbSe4 system, which is gaining significant recognition as a potential high-performance earth abundant thermoelectric material. A number of strategies have been previously reported to synthesize Cu3SbSe4 including mechanical alloying, co-precipitation, melting or fusion of elements, among other methods. High device performance has only been demonstrated after hot pressing or spark plasma sintering of the powders or films. The performance of the Cu3SbSe4 system has been improved by creating solid solutions of the sulfur and selenium materials forming Cu3Sb(S,Se)4. While some success has also been achieved by doping Cu3SbSe4 with other elements, such as bismuth or tin, resulting in increased carrier transport and decreased thermal conductivity, for such a material system to be industrially viable, further improvements are needed to increase the thermoelectric device performance, as well as utilize a more scalable synthesis and sintering process. The present novel technology addresses these needs.